The operation of heaving the ship down on one side, by arranging the ballast, or the application of a strong purchase to her masts, which require to be expressly supported for the occasion to prevent their springing; by these means one side of the bottom, elevated above the surface of the water, may be cleansed or repaired. (See breaming.) But this operation is now nearly superseded by sheathing ships with copper, whereby they keep a clean bottom for several years.